This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-369776 filed on Dec. 4, 2001.
1. Field of the Invention
The present invention relates to a fuel injection pump of an internal combustion engine (hereinafter, simply referred to as xe2x80x9cenginexe2x80x9d).
2. Description of Related Art
For example, a previously proposed common rail type fuel injection system for a diesel engine has a fuel injection pump for supplying pressurized fuel to a common rail. The fuel injection pump is driven by a drive shaft connected to a crankshaft of the engine. Rotational movement of the drive shaft is translated into reciprocal movement, for example, by a cam and is then transmitted to a plunger reciprocably supported in a cylinder. When the plunger is reciprocated, fuel in the pressurizing chamber is pressurized. A feed pump assembly, which supplies fuel to the pressurizing chamber, is integrated into the fuel injection pump. The feed pump assembly is also driven through rotation of the drive shaft to suction fuel from a fuel tank and discharges the fuel to the pressurizing chamber.
In the above described fuel injection pump, sliding surfaces are provided in the interior of a housing that defines the cylinder. More specifically, the sliding surfaces are provided, for example, between the cam and the plunger or between the plunger and a portion of the housing, which defines the cylinder. Thus, the fuel discharged from the feed pump assembly is not only supplied to the pressurizing chamber but is also supplied to the interior of the housing to lubricate the corresponding sliding surfaces of the sliding components.
In the previously proposed fuel injection pump, the fuel discharged from the feed pump assembly is supplied to the interior of the housing through a fuel passage, which extends through the housing.
However, in the previously proposed fuel injection pump, the lubricating fuel is supplied to the receiving chamber, which receives the cam, so that it is required to form an elongated through hole, which has a relatively small open cross-sectional area and extends from the feed pump assembly to the receiving chamber through the housing for supplying fuel. Furthermore, an orifice (or choke), which restrains a flow rate of fuel supplied to the receiving chamber, is formed in the fuel passage. Thus, manufacturing of such a fuel passage is tedious and time consuming, and a structure of the housing is accordingly complicated.
Furthermore, it is desirable to improve or increase a fuel injection pressure to improve engine power and also to reduce the amount of NOx emissions from the engine. However, when the fuel injection pressure is increased, a pressure applied to each corresponding component of the fuel injection pump is increased. Thus, lubrication of the sliding surfaces of the corresponding components of the fuel injection pump needs to be improved to restrain seizing of these components. In the fuel injection pump, the drive shaft is supported by the housing, so that lubrication is required not only between the cam and the plunger but is also required between the drive shaft and the housing.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a fuel injection pump, which has a simple structure and is capable of restraining seizing of its drive shaft and also capable of increasing a fuel discharge pressure.
To achieve the objective of the present invention, there is provided a fuel injection pump including at least one movable member for pressurizing fuel, a drive mechanism, a housing, a feed pump assembly, and a tubular member. The drive mechanism drives the at least one movable member and includes a drive shaft. The housing includes at least one cylinder and a receiving chamber, which are communicated with each other. Each cylinder reciprocably supports a corresponding one of the at least one movable member therein and defines a pressurizing chamber in cooperation with the corresponding movable member. The receiving chamber receives the drive mechanism. The feed pump assembly is driven by the drive shaft and pumps fuel to the pressurizing chamber. The feed pump assembly includes a discharge port, through which pressurized fuel is discharged from the feed pump assembly toward the pressurizing chamber. The tubular member is arranged between the drive shaft and the housing in a radial direction of the drive shaft and includes a fuel groove formed in an inner wall of the tubular member, which is in sliding contact with the drive shaft. The fuel groove communicates between the discharge port and the receiving chamber.